Heretofore, as a catheter equipped with an expansible member for expanding a stricture portion inside a blood vessel, there has been so-called Gruentich type disclosed, for example, in U.S. Pat. No. 4,195,637. Further, there has been used a so-called Simpson-Robert type as disclosed, for example, in U.S. Pat. No. 4,323,071.
Previously, adaptible cases for vasodilatation have been locallized stricture near coronary artery from an anatomical point of view and it has been restricted, for example, to lesion of about 15-20 mm length, monobranched lesion, not-calcified lesion, etc. Then, for enlarging the range of the adaptible cases further, a catheter equipped with an expansible member of a low profile shape having the same structure but narrowed only at the tip has been considered in addition to the standard type of the above-mentioned type, which can be adaptible to the stricture in the peripheral blood vessel or to the severer stricture (sub-complete clogging).
The so-called Gruentich type catheter as described above is formed with a catheter tube having two lumens and an expansible member attached near the tip thereof. Then, one of the lumens opens at the tip of the catheter to constitute a channel for a guide wire and a tip pressure measurement. The other of the lumens is in communication with the inside of the expansible member on the base end thereof, to constitute a flow channel for a vasographic contrast media etc. under pressure, there expanding the expansible member. Then, the catheter is formed with flexible synthetic resin.
Further, the so-called Simpson-Robert type catheter has a coaxial double walled structure comprising an inner tube having a first lumen whose tip is open and an outer tube allowing the inner tube to be inserted to the inside thereof and, further, having an expansible member being attached to the tip thereof, in which a second lumen is formed between the inner surface of the outer tube and the outer surface of the inner tube. Then, an ultrafine metal pipe is disposed in the second lumen for removing bubbles. Also in the catheter of this type, like that the so-called Gruentich type, the catheter for the vasodilation of the blood vessel is made of a flexible synthetic resin.
As has been described above, the catheter is made of the flexible synthetic resin so that it can be inserted safely to the inside of the blood vessel. Since it is formed with the flexible synthetic resin, it can be inserted into the blood vessel and, moreover, gives less damages to the blood vessel walls. On the other hand, the flexibility may cause flection of the catheter during insertion into the blood vessel. Furthermore, for displacing and rotating the tip of the catheter in a delicate manner, the catheter is moved forward-to-backward or rotated in a delicate fashion at the proximal portion, thereby transmitting the torque to the tip. Further, for inserting the tip and, further, the expansible member of the catheter into the stricture portion of the blood vessel, the operation for enforcing the catheter is applied at the proximal portion of the catheter. However, there has been a drawback that the torque and the enforcing force are absorbed by the flexibility of the catheter and, thus, are less transmitted as far as the tip, to worsen the fine operationability.
In view of the above, the object of the present invention is to provide a catheter equipped with an expansible member with no risk of flection during insertion to the inside of the blood vessel, having high transmission efficiency of the torque and the enforcing force given to the proximal portion of the catheter and of excellent operationability.
Further, a conventional double-walled tube type catheter equipped with an expansible member, has been produced by forming the outer tube and the expansible member integrally and securing the tip of the expansible member on the extension of the outer tube to the tip of the inner tube.
Further, a so-called double-lumen catheter having a second lumen in the wall of a tubular member forming the catheter has been produced by inserting an extension tube from the tip to the inside of either one of the lumens of the tubular member, securing the tip of an expansible member to the tip of the extending tube, and securing the proximal portion of the expansible member to the tip of the double lumen catheter.
In addition, as a method of producing a catheter equipped with an expansible member for dilatating a stricture portion in an endotract, there has been a method of producing a catheter equipped with an expansible member referred to a Simpson-Robert type, for example, as disclosed in U.S. Pat. No. 4,411,055. According to the description of U.S. patent specification, an expansible member is disposed integrally to the tip of an outer tube forming a second lumen for fluid for expanding the expansible member between it and an inner tube whose tip is open for forming a first lumen, in which the expansible member is formed in the course of the production steps by closing the tip of the outer tube, heating the vicinity on the proximal portion of the closed portion and applying pressure from the proximal portion.
However, in the former method, since the expansible member is formed integrally with the outer tube, it has been difficult to provide the catheter and the expansible member with physical properties required respectively therefor. In addition, there has been a great possibility that the length and the thickness of the expansible member are not sufficiently made uniform and the reproducibility for the outer diameter of the expansible member upon expansion has not completely been satisfactory. Further, the latter method requires a step of fitting and securing an extending tube whose tip is open to the tip of one of the double lumens, which makes the operation complicate.
Further, in the conventional production method, it has also been difficult to form an expansible member of uniform wall thickness.
In view of the above, it is an object of the present invention to provide a method of producing a catheter equipped with an expansible member capable of optionally setting the length and the wall thickness of the expansible member, as well as easily producing a catheter equipped with an expansible member.
A further object of the present invention is to provide a method of producing an expansible member used for a catheter equipped with an expansible member, by which the length and the wall thickness of the expansible member can be made uniform and which can produce an expansible member with high reproducibility for the outer diameter of the expansible member upon inflation.